I downloaded the trial version of David. Then a bought the license. I downloaded the voice. But even though the licensed version has installed properly I still get the interupting message that says to please get the licensed version every few seconds.

As of version 5.1 of the Cepstral voices, there is no such thing as a trial version of a voice. There is only unlicensed, then subsequently licensed voices. The unlicensed version is only different in that it speaks the license reminder. Once the user receives the email with the voice key and enters the license as described below, the reminder is removed when the voice speaks. Otherwise the voices run the same. Please note that the reminder does not obey the speech settings (it won't speed up or slow down, for instance).

On Windows: use the control panel -> Cepstral Tools panel. Make sure it is at the appropriate privilege level. Windows XP requires that you be a member of the Administrator group, but Vista and Windows 7 require that you further "Run as administrator...". There is a defect in the Vista and Windows 7: when Cepstral tools is not invoked using "Run As Administrator...", both operating systems fail silently to write the license file, which will cause the voice to revert mysteriously at some later to being unlicensed.

On linux and unix variants: users need to use the swift command line (which is also available on Windows and Mac). Run

swift --reg-voice

and enter the license information.

On the Mac: use the Cepstral Voices Preference Pane.

For all platforms:
Information is all case sensitive, punctuation sensitive.
The letters l and O never appear in the key (It's a hex entity, so it's always the numbers 0 and 1).
The 16kHz Allison voice is called "Allison" whereas 8kHz Allison is called "Allison-8kHz", and so forth for the other voices.
Keys are not interchangeable between 16 and 8kHz voices, so please make sure you downloaded the right voice, and bought the right license key for it.

We hope this helps, but if it does not, perhaps a little more detail on the situation might be in order (operating system, etc...)